The purpose of the present research proposal is to continue a comparative study of morphogenetic events associated with differentiating and undifferentiated cells by use of the techniques of light and electron microscopy (such as cytochemistry, electron cyto- and histochemistry, electron microscopic radioautography). The comparative approach to the study of cells offers the potential of finding an organism which contains the attributes needed for answering particular questions as well as finding some common morphological, physiological and biochemical denominator which is enjoyed by all organisms. The proposed studies should provide additional information as to the methods of origin, variations in activity, and functional significance of cellular organelles and their relationship to growth and development. The proposed investigations have as their ultimate long term goal the correlation of the submicroscopic structure of protoplasm with the general and specific physiology of the cell.